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Effects of a microplastic exposure gradient on juvenile lake trout (Salvelinus namaycush)
Summary
Researchers exposed newly hatched lake trout to a gradient of three microplastic types over 12 weeks, assessing growth, survival, and physiological biomarkers. Microplastic exposure caused dose-dependent effects on early life stage fish, with polymer type influencing the pattern of harm.
Growing evidence shows that microplastics have adverse impacts on fishes, but responses at the early life stages of common sportfishes are largely unknown. During a 12-week experiment, newly-hatched lake trout (Salvelinus namaycush) were exposed to three types of microplastics (polyethylene, polystyrene, and polyethylene tetraphthalate) varying in buoyancy across a range of nominal concentrations (0, 2, 35, 315, and 22465 particles/L). Microplastics included common chemical additives (metals, antioxidants and UV-stabilizers. We also included a treatment at the highest concentration to evaluate potential differences between chemical and physical effects. Concentrations in muscle tissue and gastrointestinal (GI) tracts of fish scaled positively with concentrations of microplastics. At the highest concentrations, mean counts of plastics were significantly greater in fish exposed to additives than those without. Overall, high-density polyethylene tetraphthalate (PET) was observed more commonly in fish muscle and GI tracts than polystyrene. Behavioural analysis showed that this was because juvenile lake trout spent most of their time at the bottoms of tanks, where they would have been more likely to encounter negatively-buoyant PET. Lake trout routine metabolism increased with increasing microplastic concentrations and was significantly greater than the control at the highest additive-plastic exposure concentration. Mean final mass of fish was slightly greater—and observed feeding lower—at moderate exposures or microplastics compared to control and high exposures. Proteomic analyses of exposed lake trout indicated changes in lake trout related to metabolism, cell signaling, oxidative stress, chemical exposure, and immune function. Overall, our study demonstrated significant MP accumulation in larval lake trout corresponding to their relative position in the water column, as well as some evidence of both metabolic impacts which could alter energy allocation to growth and reproduction later in life. Also see: https://micro2024.sciencesconf.org/558584/document